1. Field of the Invention
The present invention relates to a novel silver halide color photosensitive material and a method for forming color images through use of the same.
2. Description of the Related Art
Recently, the development of photosensitive materials using silver halide has markedly advanced, high-quality color images are now obtained easily. In ordinary color photography, photography is done using a color negative, and image information recorded on a color negative which has undergone development is printed optically onto photographic color printing paper to obtain color prints. This process has become highly developed in recent years, resulting in the popularization of color laboratories, or large-scale facilities for producing large numbers of color prints highly efficiently, and so-called minilaboratories, or simple, compact printer-processors installed in shops, thus making it possible for anyone to readily enjoy color photography.
The principle of currently popular color photography employs the subtractive color process for reproducing colors. An ordinary color negative comprises a transparent support provided with light-sensitive layers thereon, each of which comprises a silver halide emulsion and a so-called color coupler, the silver halide emulsions being light-sensitive elements which have individual sensitivity in blue, green, and red regions, and the color couplers functioning to form dyes of yellow, magenta, and cyan, each having the relationship of a complementary color for respective light-sensitivities. A color negative is exposed imagewise in photography and is then developed in a color developer, which comprises aromatic primary amine serving as a developing agent. In this step, exposed silver halide grains are developed or reduced with the developing agent, and the oxidized product of the developing agent (the oxidized product is formed concurrently with reduction) and the above-described color coupler undergo a coupling reaction to form dyes of individual colors. Metallic silver (developed silver) formed through development and unreacted silver halide are removed by bleach-fixing, thereby to obtain dyeimages. Color-photographic printing paper, i.e., a color photosensitive material comprising a reflective support provided with light-sensitive layers thereon, each of which has a combination of a photosensitive wavelength region and a color to be developed as does a color negative, is exposed to light which has passed through a developed color negative, followed by color development and bleach-fixing similar to those employed for a color negative. Thus, color prints are obtained, each of which comprises a dye image which reproduces an original scene.
Requests are growing for the simplification of these currently popular color image formation systems. First of all, in conducting the above-described color development and bleach-fixing, the compositions and temperature of relevant baths must be accurately controlled, requiring special knowledge and skills in operation. Second, these processing solutions contain environmentally regulated substances, such as color developing agents and the iron chelate compound serving as a bleaching agent, and thus developing equipment must be designed to regulate these waste substances. Third, the time required for development processing has been shortened through recent technological advances, but still is not short enough to meet requests for the rapid reproduction of recorded images.
Under the circumstances, to lighten the environmental load and to simplify the color image formation process, requests are increasing for a color image formation system which does not use currently used color developing and bleaching agents.
In light of the aforementioned problems, various improved techniques have been proposed. Page 180 of the IS & T 48th Annual Conference Proceedings, for example, discloses a system in which dyes generated through a development reaction are transferred to a mordant layer, and the mordant layer is then separated, thereby removing developed silver and unreacted silver halide, making the bleach-fix bathing conventionally required for photographic processing unnecessary. The proposed technique still requires development processing in a processing bath which contains a color developing agent, however. Thus, the above-mentioned environmental problems, cannot be said to have been solved yet.
As a system that does not require a processing solution that includes a color developing agent, Fuji Photo Film Co., Ltd., provides the Pictography system. In this system, a small amount of water is supplied to a light-sensitive member which contains a small amount of base precursors. The light-sensitive member is placed onto an image-receiving member, and the resulting assembly is heated to initiate a development reaction. This system is environmentally advantageous because it does not use the aforementioned processing bath. In this system, however, the thus-formed dyes are fixed in a dye-fixing layer to form dye images to be viewed. Therefore, it is desired to develop a system capable of applying this technique to recording materials for photograph-taking use. To be used as the material for photograph-taking-use, the silver halide emulsion used must have high sensitivity, excellent granularity, and excellent pressure resistance.
A technique for improving the sensitivity and granularity of the silver halide emulsion uses tabular grains. Techniques for using tabular grains in heat development system are disclosed in U.S. Pat. No. 4,435,499, Japanese Patent Application Publication (JP-B) No. 2-48101, Japanese Patent Application Laid-Open (JP-A) Nos. 61-77048, 62-78555, and 62-79447.
Studies conducted by the present inventors, however, have revealed that, compared to the case with liquid development, pressure fogging is a far worse problem in heat development which uses a silver halide emulsion comprising tabular silver halide grains in accordance with the above-mentioned technique.
Pressure fogging is caused, for example, by a grain of sand getting into a camera and coming in contact with the emulsion side of film. When pressure is applied to the portion of contact during film travel, the portion of the film to which pressure is applied becomes fogged. This fogging appears as a problem in the form of a scratch in an image area, making the reduction of pressure fogging highly desirable.